The demand for biosensors measuring the amount or concentration of biological entities is increasingly growing these days. Usually, biosensors allow for the detection of a given specific molecule or target analyte within a small sample volume, wherein the amount of said molecule is typically small. For example, one may measure the amount of drugs or cardiac markers within saliva or blood. Therefore, label particles, for example super-paramagnetic beads, are used which bind to a specific binding site or active surface only, if the molecule to be detected is present within the sample. One recent technique to detect these label particles bound to the active surface is frustrated total internal reflection (FTIR). Therein, light is coupled into the disposable substrate such that it illuminates the active surface from the inside at an angle of total internal reflection. If no particles are present close to the active surface, the light is completely reflected. If, however, label particles are bound to said surface, the evanescent field extending in the sample fluid is scattered by or coupled into the super-paramagnetic label. A portion of the light is scattered into the sample or absorbed by the particle and thus the amount of light reflected by the surface is decreased. By measuring the intensity of the reflected light with an optical detector, it is possible to estimate the amount of particles bound to the surface. This allows for an estimate of the amount of the specific molecules of interest present within the sample fluid. For point of care applications biosensors having small measures for a comfortable use are aimed for, e.g. biosensor devices held in a hand. Other biosensor devices are rather designed for use on desk top, these are mostly immobile on the desk top surface and for laboratory use, commonly operated by skilled personnel. Measurement devices comprising biosensors now are designed either for handheld use in point of care applications or for laboratory use.